Add missing Audio() constructor; fix moz* versions (#4908)
Add missing Audio() constructor; fix moz* versions (#4908)

* Add missing Audio() constructor; fix moz* versions
This update adds the missing `Audio()` constructor
to `HTMLAudioElement`. It also corrects version
information for the Mozilla-specific methods; they
were all removed way back in Firefox 31. Other minor
version tweaks have been made as well.

Sources:
* Removal of moz* methods: https://bugzilla.mozilla.org/show_bug.cgi?id=927245

* Fixed per feedback

chrisdavidmills/browser-compat-data,chrisdavidmills/browser-compat-data,mdn/browser-compat-data,mdn/browser-compat-data